For the past 15 years, the principal goal of my research program has been to elucidate the biological differences between tobacco-induced squamous cell carcinomas (SCC) of the upper aero-digestive tract (ADT) or cervix uteri and normal keratinocytes. Since our discovery in 1989 that most if not all SCC cell lines are refractory to Transforming Growth Factor-beta (TGFbeta)-mediated cell cycle arrest, we have focused specifically on elucidating the molecular mechanism underlying this phenotype. My long term goal is to use this information to develop novel approaches to the prevention and treatment of ADT cancers which still account for as many cancer deaths as 30 years ago. During the past 3 years, we have made significant progress. We were the first to identify missense mutations in the TGFbeta type II receptor (TbetaR-II) gene in head-&-neck SCC cells that nearly complete abrogate TbetaR-II kinase activity and signaling, and a novel nonsense mutation that encodes a truncated soluble TbetaR-II receptor in a cervical carcinoma. In addition, loss of mRNA expression of TbetaR-II accounts for TGFbeta resistance in approximately 25% of esophageal carcinomas and in nearly all small cell lung carcinoma (SCLC) cell lines. In this study, we have identified an in-frame deletion of 3 repeating GGC trinucleotides in exon 1 in 6 of 16 cases that probably affects the receptor processing and appear to confer an increased risk for the development of cervical cancer. Our specific goals for the coming five years are: 1. To develop and refine the reagents and assays necessary to evaluate the molecular and functional status of the TGFbeta signaling pathway in carcinoma tissue specimens in a comprehensive fashion. 2. To determine at which stage of tumor development and progression the TGFbeta signaling pathway becomes inactivated, and whether or not the emergence of TGFbeta-resistant clones is tied to the presence of a biologically active TGFbeta in the tumor microenvironment. 3. To determine how cancer-associated mutations in TGFbeta receptor genes alter the biochemical and biological properties of the receptors. 4. To develop novel therapeutic strategies designed to activate the TGFbeta signaling pathway downstream of functionally deficient TbetaR receptors.